Long-term cervical sagittal balance after single-level anterior cervical discectomy with or without fusion or arthroplasty: sex-specific changes in cervical alignment over 5 years.

BACKGROUND CONTEXT: Cervical sagittal balance influences spinal biomechanics and may be affected by anterior cervical discectomy (ACD), potentially affecting clinical outcomes.

PURPOSE: To evaluate longitudinal changes in cervical sagittal alignment over 5 years following single-level ACD with or without fusion or arthroplasty and assess associations with clinical outcomes.

PATIENT SAMPLE: Patients undergoing single-level ACD with or without fusion or arthroplasty for cervical radiculopathy were evaluated at baseline, 1-, 2-, and 5-years follow-up.

OUTCOME MEASURES: C0-C2 angle, C2-C7 Cobb angle, segmental Cobb angle, C7 angle, T1 angle, T1-CL (T1 angle minus C2-C7 lordosis) and C2-C7 sagittal vertical axis (SVA) were measured on lateral radiographs. Clinical outcomes included the Neck Disability Index (NDI) and Visual Analog Scale (VAS) for arm and neck pain.

METHODS: Linear mixed models assessed longitudinal changes, corrected for potential confounders. Linear regression evaluated associations between alignment and clinical outcomes.

RESULTS: Out of 109 enrolled patients, 81 patients had a lateral X-ray available at baseline. C2-C7 Cobb angle increased from 9.0° at baseline to 13.8°, 12.3°, and 13.6° at 1-, 2-, and 5-year follow-up (p<0.001). T1-CL decreased from 12.5° to 4.7°, 6.4°, and 6.8° (p<0.05). SVA decreased from 16.1 mm to 10.5 and 10.7 mm at 1 and 2 years (p<0.05), returning to 14.8 mm at 5 years. C0-C2 angle increased from 19.4° at 1 year to 23.1° at 5 years (p<0.005). Men showed greater subaxial lordosis; women greater upper cervical lordosis. At 1 year, a more positive segmental Cobb angle was associated with lower arm pain (B=-1.99, p=0.02) and higher SVA with increased arm pain (B=0.48, p=0.04).

CONCLUSIONS: Single-level ACD with or without fusion or arthroplasty is associated with long-term increases in cervical lordosis with sex-specific compensatory patterns. Alignment-outcome cross-sectional associations were limited to early follow-up, suggesting that restoring adequate segmental lordosis at surgery may reduce early postoperative arm pain.

STUDY DESIGN: Post hoc analysis of the Netherlands Cervical Kinematics (NECK) trial (NTR1289).